Part 4 – Installing the Polini Upgear Kit
One of the complaints often heard from those who have installed the Malossi 190 cylinder kit is that – although it dramatically increases torque to allow for quicker acceleration – it does not allow significantly higher top speeds because of engine rpm limitations. In an effort to make my LX more versatile by improving all aspects of its performance – including top end – I figured I could exploit some of that increased torque to increase top speed significantly by going to taller final gearing while I had the engine out of the bike anyway. To that end, I installed the Polini upgear kit.
A word of caution. If you are not installing a cylinder kit to significantly increase your torque, don’t waste your money on the upgear kit. Installing it with the stock engine will only decrease your acceleration capability and may actually reduce your top speed, as the stock engine won’t produce enough horsepower to exploit the taller gearing.
Although I did the upgear kit installation at the same time as I installed the cylinder kit, you don’t have to. It can be done with the engine still in the scooter. You’ll need to remove the exhaust system and rear wheel, as well as the transmission cover and clutch assembly to get at the final drive parts, but that is all that is necessary.
With the engine out of the scooter and the transmission cooling duct and airbox already out of the way, removing the transmission cover involves only removing the driven (clutch) shaft nut and the perimeter screws. To loosen the driven shaft nut, it is necessary to immobilize the clutch assembly with a clutch holding tool. Once the transmission cover is off, simply slide the clutch assembly off its shaft and set it aside.
The first step in actually installing the upgear kit is to drain the gearbox oil:
Remove the brake shoes by folding them outward toward each other and pulling them free of the actuating cam and pivot pin (note that the brake shoes have to come off, as one of the cap screws holding the gearbox cover on is beneath the upper shoe):
I removed the brake lever and cam to lubricate them, but I guess that wouldn’t really be necessary just to install the kit:
To open up the gearbox, remove the cap screws securing the cover:
… and carefully slide the cover off. The intermediate gear shaft and rear axle shaft/gear will come free with the cover:
Remove the intermediate gear shaft:
The larger spur gear on this shaft will need to be pressed off at a machine shop with a large-capacity hydraulic press and replaced with the one that comes with the upgear kit. Forget about trying to use a simple arbor press or heating/cooling methods as this is a really tight interference fit. A big press is necessary, so go straight to a machine shop. I paid $20 to have the old gear pressed off and the new one pressed on while I waited.
Slide out the driven shaft, taking extreme care not to damage the oil seal as you remove the shaft:
Once you are back from the machine shop, insert the new driven shaft with its slightly larger gear that comes with the kit (again with care not to damage the seal), and insert the intermediate shaft with its newly installed spur gear:
Apply some gear oil to the gears and reinstall the gearbox cover:
Torque the cover screws to spec… and don’t make fun of my ancient beam-type torque wrench that served me well for over 40 years (I’ve since replaced it with a modern “click” type):
Refill the gearbox with the specified amount of gear oil. Before replacing the clutch assembly and tranny cover, give the driven shaft a spin with your fingers to make sure everything turns smoothly:
That’s it for the actual upgear kit installation. In Part 5, I’ll talk about variator tuning to get the most out of the engine and gearing mods.
Last edited by Silver Streak on Mon Feb 15, 2010 6:05 pm; edited 1 time in total